1. Field of the Invention
The invention refers to a preservative for pharmaceutical products, especially for ophthalmic pharmaceuticals, nasal spray, ear drops and corresponding veterinary products.
Pharmaceutical products in the form of solutions, suspensions or ointments which are applied directly from a container may get in contact with the body fluids of the user or microorganisms of the environment. Therefore, there is a danger of contamination of the product in the container by bacteria contained in the body fluid. On the other hand the use of preservatives in pharmaceuticals is limited in that any interference with the pharmaceutically active ingredients and any noxious effect to the user is to be avoided.
2. Description of the Prior Art
Especially for preserving ophthalmic pharmaceuticals it has been well documented in the literature that benzalkonium chloride, chlorobutanol, thimerosal, methyl and propyl parabens have many drawbacks and disadvantages. The most common complaints included burning, stinging, and irritation upon instillation. Also, there is a 5% to 15% incidence of allergic reactions to these preservatives. Thimerosal has been shown to exhibit an allergic response as high as 20% in some studies. Thimerosal is a mercurial derivative, therefore, has raised concerns for long-term usage as well. As a result of allergic reactions to thimerosal, almost all ophthalmic products that contained thimerosal have had formulation changes to one of the other available preservatives.
Another characteristic of these preservatives is that they have been shown to cause a disruption of the cornea epithelium upon instillation. Documentation via SEM (scanning electron microscopy) has demonstrated these epithelial changes in the literature.
Obviously, a lot of other preservative substances are known for several purposes and applications. Among them a sodium silver chloride compound has been used for sterilizing water, especially drinking water, and other aqueous solutions as e.g. homeopathic solutions.